Synthetic polymers have properties which make them suitable for many applications in industry. Because of their properties, such as elasticity, light weight and compatibility with living tissue, they are particularly useful in the preparation of products in the medical field, such as artificial valves, veins, tubes, catheters, and the like.
In many applications, and particularly those in the medical field, the friction characteristics of the polymer product are important as in many cases the polymer product must move with respect to some other surface which may include another polymer, biological or other solid or semi-solid surface. This is particularly true in the case of double slideable catheters or guided catheters wherein one tube or catheter must move within the lumen of a second outer tube or catheter or wherein the outer tube or catheter must move over an inner tube or rod, including metal or polymer guides.
Catheters prepared from synthetic polymers have gained widespread acceptance by the medical profession. Catheters are used frequently in such routine procedures as the delivery of intravenous fluids and the removeal of urine from compromised patients. Cardiovascular dynamics are increasingly monitored utilizing catheter systems. Catheters are in use and being developed for chemical sensing using a variety of chemical transducers. Such catheters provide the pathway by which heretofore inaccesible body areas can be reached for both diagnostic and therapeutic procedures, thereby reducing the need for surgery.
As catheterization techniques have become more complicated, demands placed on the performance of the catheter have increased proportionately. Whereas catheters were once little more than straight plastic tubes, they are now available in a variety of configurations. Some are highly specialized with unique apertures, appendages, and tapers, and may even employ fiberoptics.
Recently, double catheter systems have been employed to deliver drugs or occlude blood flow to specific organs or tissues. These systems usually employ a rigid outer catheter and a buoyant, flexible inner catheter than can freely float in the blood stream.
The paths that these catheters must take through the body are often long and tortuous. For example, in order to access the cranial vessels, catheterization may be initiated at the femoral artery. There is a great deal of surface contact between the two catheters and a great deal of friction can, and often does, result. The frictional drag encountered by the inner catheter as it slides through the outer catheter makes its placement difficult and sometimes impossible.
Various methods have been proposed in the past for reducing the friction resistance characteristics of polymer and other surfaces, such as the addition of lubricants, polishing of the surface, etc., but none has been entirely satisfactory, particularly for medical products, such as double slideable catheters. In some cases, the treatment has had a detrimental effect on the movement of the inner catheter and in some cases the treatment has been only temporary or has had a detrimental reaction with body materials in contact with the catheter.
Improved technics for treatment of polymer surfaces to reduce friction resistance are disclosed in an article by Triolo et al published in Journal of Biomedical Materials Research, Vol. 17, 129-147 and 149-165 (1983).
It is an object of the invention, therefore, to provide a new and efficient process for reducing friction resistance characteristics of polymer surfaces when in contact with non-polar liquids, such as water, as in the case of medical products, such as catheters, where the increased movability and water wetability are greatly needed. It is a further object to provide treated surfaces which have good biocompatibility with body materials, such as blood plasma and the like.